Contract #561 — campaign composition: includes, attachments, copy

[The-Running-Dev]

Contracts campaign composition for #561, following the composition-at-load decision recorded for #293/#292 in #562. This PR changes documents only; W120 builds it.

Core (04):

• §10.4. Adds CampaignInclude/CampaignAttachment and their siblings, with the split between what the core checks and what the kind checks.
• Fixed order. Composition runs depth-first, in a fixed order.
• Version pins. Pins check the authored version, not the stamped one.
• §3. Adds Kind.composeContent.
• §12. Adds seven core codes.
• C17 and §17. : is allowed in composed ids only.

Story-graph (03):

• §1.1. Adds the module block, the include binding and the attachment payload. A module's exits are its endings, and the entry is an auto node whose id is the alias.
• §5. Adds a new copy consequence.
• §8.3. Adds six codes.

Packs (11):

• §2 and §3a. Adds ContentPack.attachments and ResolvedRegistry.authoredVersions.
• §6. The digest changes only when includes or attachments are non-empty.

Decisions: a 90-decisions.md entry records all nine answers, the drafting calls and the rejected options. It names the four answers where the owner chose against the recommended option.

Open, not decided here:

• The portable format does not carry includes.
• SubZeroDev.Adventures may check id shapes, and the : amendment widens them.

Verified:

• ./build/Test-Documentation.ps1 passed: 131 files, and the drift check across 18 generated pages and the guide.
• git diff --check is clean.
• Not run: the engine typecheck/lint/test (this PR changes no code), and ./docs.ps1 -BuildOnly. The Verify Documentation Build check covers the Docusaurus build.